1. Field of the Invention
The present invention generally relates to a method for fabricating a thin metal shell, and more particularly to a method for fabricating a thin metal shell having connecting components.
2. Description of the Prior Art
As the trends in household appliance, consumer electronics, computers and peripheral equipment move towards much lighter, thinner, shorter and smaller requirements, particularly the requirements for the portable products, are even stringent. Therefore, it strongly requires to use much lighter materials for the structural components (like frame, shield and partition plate) of the products in order to meet these requirements. Hence, in the early stage manufacturers of fabricating household appliance, consumer electronics, computers, and peripheral equipment utilize the plastic injection molding to fabricate the shell massively. They also dispose the mortise, tenon, slot, positioning pin/hole, reinforced rib, partition wall and sinking or bulge match components to rapidly connect, position and decrease the usage of the screws and action of screwing during the assembly process. However, plastic materials have the problems of low structural strength. These materials are easily fractured and scratched upon external impact and the decrease in size for the screw hole bases or the positioning pins is limited, otherwise they are easily fractured and broken. In addition, the plastic component has an electromagnetic interference (EMI) problem and thus the surface of the plastic component must do certain treatment to prevent EMI. This treatment will increase the cost of manufacturing.
Recently, applications of light metals have been tremendously increased to replace the plastic materials for manufacturing the shell components. These light materials used for manufacturing the shell components, such as magnesium (Mg) alloy, aluminum (Al) alloy and Titanium (Ti) alloy, have a high structural strength and can be made very thin. In addition, these alloys provide a better EMI protection and can be recycled. For example, U.S. Pat. No. 5,237,486 entitled xe2x80x9cStructure Frame for Portable Computerxe2x80x9d issued to LaPointe et. al. on Aug. 17, 1993 discloses a lightweight die-cast magnesium (Mg) alloy frame of the portable computer with the advantages of high structural strength, thinness, EMI protection. However, the technology of die casting or thixomolding for fabricating the thin shell components utilized in the U.S. Pat. No. 5,237,486 and in the current industry has a weakness of low yield rate. The yield rate is less than 60% and the thickness of A4 size shell cannot be less than 1 mm. Besides, the surface of the thin shell components by the die casting method usually has pores, voids or cracks. These imperfections need to be reworked by filling and multiple layer surface treatment so as to obtain delicate appearance. So, the cost will be very high.
Except the die casting method, manufacturers try to use the forging method to fabricate the thin metal shell components. This method has been successfully applied to thin metal shell components with small size, such as the shield of MD case (80xc3x9780 mm). However, there still exists technical difficulty for making large size thin metal shell components. In addition, no matter the thin metal shell components made by either the die casting or the forging method, the components need further mechanical machining (such as milling and tapping) to form connecting components thereon, which significantly increases the cost of manufacturing. Besides, flammable metals (like Mg alloy) are liable to burn during the processes of melting and refining, and mechanical machining. It will increase the danger during the manufacturing process.
In views of the disadvantages of low yield rate, limited size for thin metal shell components and danger during the manufacturing process according to the above-mentioned methods, there is a need to develop a new method for manufacturing the thin metal shell in order to overcome the above-mentioned disadvantages.
An object of the invention is to provide a method for fabricating the thin metal shell having connecting components, in which the present method can tremendously decrease the technical difficulty of fabricating the thin metal shell and make the subsequent surface treatment or coating processes become much easier, thereby decreasing the manufacturing cost.
Another object of the invention is to provide a method for fabricating the thin metal shell having connecting components, which utilizes the bonding technology to bond components tightly and does not need additional mechanical machining.
Another object of the invention is to provide a method for fabricating the thin metal shell having connecting components, in which the present method can get rid of the danger of using flammable alloys during the process of melting, refining, and mechanical machining, thereby improving the safety during manufacturing process.
Another object of the invention is to provide a method for fabricating the thin metal shell having connecting components, in which the connecting components such as outer screws or barbs, inner slots which are difficult to be formed by current manufacturing methods.
Another object of the invention is to provide a method for fabricating the thin metal shell having connecting components for producing much larger and thinner metal shell.
Another object of the invention is to provide a method for fabricating the thin metal shell having connecting components for improving the yield rate and quality stability of metal shell so as to decrease the manufacturing cost.
According to the present invention, a metal plate is firstly formed into a thin shell by plastic forming technology, and a plurality of connecting bases are also formed on the surface of the shell component; structure adhesives are applied to the connecting bases; connecting components are disposed on the connecting bases for positioning and connecting; finally, the structure adhesives which are used to bond the shell and connecting components are cured in order to bond those components. The technologies of plastic forming suitable for the present invention include, but not limited to, stamping, forging, drawing, extruding, progressive cold forming or superplastic forming process. The metals appropriate for this method include ferrous metals such as galvanized sheet iron and stainless steel plate; nonferrous metals such as copper (Cu) alloy, aluminum (Al) alloy, magnesium (Mg) alloy, titanium (Ti) alloy, zinc (Zn) alloy, nickel (Ni), tin (Sn), aluminum-lithium (Alxe2x80x94Li) alloy or superalloys composed thereof.
According to the present invention, the methods of bonding the connecting components to the thin metal shell include spot welding, laser welding, resistance welding or ultrasonic welding.